1. Field of the Invention
The present invention relates to a plasma display panel, and more particularly, to a plasma display panel, fabricating apparatus and method thereof.
2. Discussion of the Related Art
Today""s multimedia demands displays which can represent colors with finer and greater detail with more natural looking images than those of the conventional displays. Specifically, today""s CRT (cathode ray tube) or LCD (liquid crystal display) cannot be made into large-scaled display over 40 inches, therefore a plasma display panel (hereinafter abbreviated PDP) is considered to be the next generation display.
Plasma display panels, such as the one shown in FIG. 1A, includes upper and lower plates 10 and 20 bonded to each other. FIG. 1B illustrates a cross-sectional view of a plasma display panel in FIG. 1A, in which the lower plate 20 is rotated at 90xc2x0 for the convenience of explanation.
The upper plate 10 includes scan electrodes 16 and 16xe2x80x2 and sustain electrodes 17 and 17xe2x80x2 formed in parallel with each other, a dielectric layer 11 formed on the upper plate 10 including the scan electrodes 16 and 16xe2x80x2 and sustain electrodes 17 and 17xe2x80x2, and a passivation layer 12 on the dielectric layer 11. The lower plate 20 includes address electrodes 22, a dielectric film 21 on an entire surface of a substrate including the address electrodes 22, barrier ribs 23 on the dielectric film 21 between the address electrodes 22, and a fluorescent material 24 formed on surfaces of the barrier ribs 23 and dielectric film 21 inside in each discharge cell. The space between the upper and lower plates 10 and 20 is charged with a discharge gas mixed with an inert gas such as HE, Xe and the like so as to provide a discharge area.
The PDP operates by igniting the discharge gas. Once a drive voltage is applied a discharge is generated between the address and scan electrodes so that electrons discharged from the inert gas in the discharge cell by the discharge collide with a surface of the passivation layer. Such a collision of electrons causes the electrons to be discharged secondarily from the surface of the passivation layer, then the secondary electrons collide with the plasma gas so as to diffuse the discharge. After the end of the confronting discharge between the address and scan electrodes, wall charges are formed at the surface of the passivation layer on the address and scan electrodes so as to have polarities opposite from each other.
When the drive voltage applied to the address electrode is cut off, the discharge voltage having the opposite polarities is applied continuously to the scan and sustain electrodes. A voltage difference between the scan and sustain electrodes generates a surface electric discharge from the discharge area of the dielectric and passivation layers. The confronting and surface electric discharges make the electrons existing inside the discharge cell collide with the inert gas in the discharge cell. Resultingly, the inert gas in the discharge cell becomes excited so as to generate a UV-ray having a wavelength of 147 nm in the discharge cell. Such a UV-ray collides with the fluorescent material surrounding the barrier ribs and address electrode so as to realize an image.
Hence, in order to make PDP give full play to its performance and extend its endurance, the panel should have strong layers as well as no impurity gas inside.
For convenience, a fabrication method of such PDP is mainly divided into a pre-process, an after-process, and a module process.
First, various layers are formed on the upper and lower plates 10 and 20 in the pre-process. And, the after-process includes a bonding step of the upper and lower plates 10 and 20, electric discharge gas injection and tip-off steps, an aging step, and a checking step. In this case, xe2x80x98tip-offxe2x80x99 is the step of sealing an exhaust pipe by melting after the completion of exhaust and electric discharge gas injection through the exhaust pipe, and xe2x80x98agingxe2x80x99 is the step of applying a power to electrodes for a predetermined time to drive so as to remove impurities finally as well as realize an electric discharge voltage drop effect. Circuits and packages are then assembled so as to complete the PDP in the module process.
FIG. 2 illustrates an after-process and process conditions of a plasma display panel according to a related art. FIG. 3A to FIG. 3C illustrates layouts for a bonding process in FIG. 2, FIG. 4 illustrates a cross-sectional view of an exhaust pipe, FIG. 5 illustrates a layout of a separative bonding/exhaust apparatus of a plasma display panel according to a related art, and FIG. 6 illustrates a diagram of a cart in FIG. 5.
The after-process of PDP according to the related art, as shown in FIG. 2, including bonding, exhausting, electric discharge gas injecting, tipping-off, and aging.
First, the upper and lower plates 10 and 20 are transferred to a bonding equipment. Next, a circumference of the upper plate 10, as shown in FIG. 3A, is coated with a sealant 31, i.e. frit to a predetermined thickness using a dispenser. In this case, frit consists of glass and an additive improving adhesiveness.
A drying is carried out at about 120xc2x0 C., and then a plasticizing is carried out above 400xc2x0 C. so as to remove impurities remaining in the frit. Subsequently, the upper and lower plates having completed the plasticizing are transferred to the bonding equipment. In this case, the upper plate 10 is exposed to atmosphere so as to be moved to the bonding equipment.
The upper and lower plates 10 and 20, as shown in FIG. 3B, are aligned with each other in the bonding equipment, and fixed thereto by tongs 32. The frit is then melted, as shown in FIG. 3C, so as to bond the upper and lower plates 10 and 20 to each other.
Additionally, in the bonding step, an exhaust pipe 40 like a straw made of glass, as shown in FIG. 4, is attached to an exhaust hole 42 of the lower plate 20 using a frit ring 41. Subsequently, the panel of which bonding step is completed is transferred to an exhaust and gas injection equipment.
Then, the exhaust and gas injection equipment carries out the exhaust step of discharging externally an impurity gas generated from the layers and impurities adhering to the layers on heating condition at high vacuum using the exhaust pipe 40 formed in the binding step. An electric discharge gas is then injected through the exhaust pipe 40, and then the tip-off step is carried out in a manner that a tip of the exhaust pipe 40 is heated to melt so as to prevent the injected electric discharge gas from leaking. Finally, a status of the panel is checked after the aging step so as to complete the whole process.
The separative type fabricating equipment in an exhaust type apparatus, which carries out the bonding and exhaust/gas injection steps separately, are divided into the bonding equipment and the exhaust/gas injection equipment. The exhaust/gas injection equipment, as shown in FIG. 5, includes a hot wind heating furnace 51 providing conditions for exhaust/electric discharge gas injection and a cart 52 loading the panel 33 as well as unloading the panel after the exhaust/electric discharge gas injection in the hot wind heating furnace 51.
The cart 52, as shown in FIG. 6, has a complicated structure including a vacuum pump 61 providing a panel with a vacuum state, a vacuum pipe system constructed with an exhaust manifold 62, valves, ad pipes, an electric discharge gas injection bomb 65, a gas injection pipe system constructed with a gas injection manifold 63, valves, and pipes, and a tip-off unit 64 tipping off the exhaust pipe 40.
Unfortunately, the apparatus and method for fabricating PDP have the following problems or disadvantages.
First, it takes a relatively long time (about 24 hours) to suck out the impurity gas through a several-hundred-microns gap between the bonded upper/lower plates of an at least 40-inch panel as well as inject the electric discharge gas through the gap.
Second, the panel is heated at a highly vacuum state so as to receive a huge load thereon. Since the panel is made of glass vulnerable to thermal deviation and tensile strength, the panel may be broken or degrade its characteristics.
Third, the plasticizing step is carried out to remove the impurities of the frit used for the attachment of the upper and lower plates. The heating/cooling of the plasticizing step increases its energy consumption as well as a quantity of the impurities from the frit due to the high temperature in the bonding step. Hence, the exhaust time extends. And, the frit itself is fragile to an external impact, thereby becoming one reason of the panel crack on external impact.
Fourth, the passivation layer of the upper plate according to a related art plays an important role in preventing the damage of electrodes caused by electric discharge. The passivation layer is exposed to atmosphere so as to be moved to a bonding stage. The exhaust and electric discharge gas injection steps are then carried out on the upper plate including the passivation layer. Since MgO used mainly for a passivation material is easy to combined with atmospheric components such as moistness and the like so as to be contaminated. Therefore, such a passivation layer reduces a product performance as well as endurance.
In order to overcome the above problems of the exhaust pipe system, a tip-less system, which uses no exhaust pipe, has been proposed. The tip-les system carries out the exhaust step prior to the bonding step, thereby requiring no exhaust pipe.
Yet, in the tip-les system, the bonding step should be carried out on condition that the chamber is filled with the electric discharge gas. Hence, when the frit is melt, a great deal of impurity gas is generated so as to contaminate the expensive electric discharge gas. Such a contamination makes the electric discharge gas useless fatally, whereby it is unable to apply the tip-less system to a real production.
Moreover, a semi-tip-less system, which injects the electric discharge gas through an extra-hole instead of filing the chamber with the electric discharge gas, has been proposed to prevent the above-explained contamination of the electric discharge gas. Yet, the semi-tip-les system is carried out in a manner that the injection hole is closed up with a coin-like stopper so as to be airtight by melting a frit. Hence, the impurity gas generated from the melt frit penetrates the panel internally so as to bring about the same fatal problem of the tip-less system, the contamination of the electric discharge gas. Thus, it is unable to apply the tip-less system to a real production as well.
Resultingly, the PDP fabrication method using the exhaust pipe according to the related art requires a long exhaust time due to the frit contamination and impurities remaining in the panel, thereby extending an overall product process time. Hence, a sufficient equipment space is required for mass production. And, the vacuum/highly-thermal processes, the exposure of the passivation layer to atmosphere, the deterioration of the panel, and the exhaust pipe bring about the characteristic and performance degradation inevitably.
Accordingly, the present invention is directed to a plasma display panel, fabricating apparatus and method thereof that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a plasma display panel, fabricating apparatus and method thereof enabling to reduce a process time for a PDP fabrication as well as prevent a degradation of a panel channel characteristic and panel damage.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an apparatus for fabricating a plasma display panel according to the present invention includes a passivation layer forming equipment for forming a MgO passivation layer on a first substrate, a cleaning equipment for removing impurities existing on the first substrate having the passivation layer and a second substrate and carrying out vacuum exhaust, and an electric discharge gas injection/bonding equipment for coating a sealant hardened by UV-rays on the second substrate cleaned through the cleaning equipment, irradiating the UV-rays on the second substrate attached closely to the first substrate while an electric discharge gas is injected so as to carry out a bonding between the first and second substrates.
In another aspect of the present invention, a method of fabricating a plasma display panel, which is carried out in a fabricating apparatus including first to third equipments built airtight in one body so as to carry out a passivation layer forming to an electric discharge gas injection/bonding therein, includes a passivation layer forming step of forming a MgO passivation layer on a first substrate in the first equipment, a cleaning step of transporting the first substrate having the MgO passivation layer and a second substrate to the second equipment, removing impurities existing on the first and second substrates by generating a plasma electric discharge between the first and second substrates using an electric discharge gas in the second equipment, and carrying out vacuum exhaust, and a bonding step of transporting the cleaned first and second substrates to the third equipment, coating a UV-hardening sealant on the first substrate, filing the third equipment with the electric discharge gas, attaching the first substrate closely to the second substrate, irradiating UV-rays on the sealant to be hardened so as to bond the first and second substrates to each other.
In a further aspect of the present invention, a plasma display panel using an epoxy-based sealant hardened by UV-rays so as to bond upper and lower plates to each other.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.